strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces. Also replace an instance of strcpy() which is also
deprecated.
s_volume_ident is a NUL-terminated string which is evident from its
usage in udf_debug:
| udf_debug("volIdent[] = '%s'\n", UDF_SB(sb)->s_volume_ident);
s_volume_ident should also be NUL-padded as it is copied out to
userspace:
| if (copy_to_user((char __user *)arg,
| UDF_SB(inode->i_sb)->s_volume_ident, 32))
| return -EFAULT;
Considering the above, a suitable replacement is `strscpy_pad` [2] due
to the fact that it guarantees both NUL-termination and NUL-padding on
the destination buffer.
To simplify the code, let's use the new 2-argument version of
strscpy_pad() introduced in Commit e6584c3964f2f ("string: Allow
2-argument strscpy()"). Also zero-allocate @outstr so we can safely use
a non-@ret length argument. This is just in case udf_dstrCS0toChar()
doesn't include the NUL-byte in its return length, we won't truncate
@outstr or write garbage bytes either.
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
Note: build-tested only.
Found with: $ rg "strncpy\("
---
fs/udf/super.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/udf/super.c b/fs/udf/super.c
index 2217f7ed7a49..77d32fe14434 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -895,7 +895,7 @@ static int udf_load_pvoldesc(struct super_block *sb, sector_t block)
int ret;
struct timestamp *ts;
- outstr = kmalloc(128, GFP_KERNEL);
+ outstr = kzalloc(128, GFP_KERNEL);
if (!outstr)
return -ENOMEM;
@@ -921,11 +921,11 @@ static int udf_load_pvoldesc(struct super_block *sb, sector_t block)
ret = udf_dstrCS0toChar(sb, outstr, 31, pvoldesc->volIdent, 32);
if (ret < 0) {
- strcpy(UDF_SB(sb)->s_volume_ident, "InvalidName");
+ strscpy_pad(UDF_SB(sb)->s_volume_ident, "InvalidName");
pr_warn("incorrect volume identification, setting to "
"'InvalidName'\n");
} else {
- strncpy(UDF_SB(sb)->s_volume_ident, outstr, ret);
+ strscpy_pad(UDF_SB(sb)->s_volume_ident, outstr);
}
udf_debug("volIdent[] = '%s'\n", UDF_SB(sb)->s_volume_ident);
---
base-commit: 928a87efa42302a23bb9554be081a28058495f22
change-id: 20240401-strncpy-fs-udf-super-c-983457eb4ac3
Best regards,
--
Justin Stitt <[email protected]>
On Mon 01-04-24 20:01:51, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces. Also replace an instance of strcpy() which is also
> deprecated.
>
> s_volume_ident is a NUL-terminated string which is evident from its
> usage in udf_debug:
> | udf_debug("volIdent[] = '%s'\n", UDF_SB(sb)->s_volume_ident);
>
> s_volume_ident should also be NUL-padded as it is copied out to
> userspace:
> | if (copy_to_user((char __user *)arg,
> | UDF_SB(inode->i_sb)->s_volume_ident, 32))
> | return -EFAULT;
>
> Considering the above, a suitable replacement is `strscpy_pad` [2] due
> to the fact that it guarantees both NUL-termination and NUL-padding on
> the destination buffer.
>
> To simplify the code, let's use the new 2-argument version of
> strscpy_pad() introduced in Commit e6584c3964f2f ("string: Allow
> 2-argument strscpy()"). Also zero-allocate @outstr so we can safely use
> a non-@ret length argument. This is just in case udf_dstrCS0toChar()
> doesn't include the NUL-byte in its return length, we won't truncate
> @outstr or write garbage bytes either.
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
Thanks! Added to my tree.
Honza
> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
> fs/udf/super.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/udf/super.c b/fs/udf/super.c
> index 2217f7ed7a49..77d32fe14434 100644
> --- a/fs/udf/super.c
> +++ b/fs/udf/super.c
> @@ -895,7 +895,7 @@ static int udf_load_pvoldesc(struct super_block *sb, sector_t block)
> int ret;
> struct timestamp *ts;
>
> - outstr = kmalloc(128, GFP_KERNEL);
> + outstr = kzalloc(128, GFP_KERNEL);
> if (!outstr)
> return -ENOMEM;
>
> @@ -921,11 +921,11 @@ static int udf_load_pvoldesc(struct super_block *sb, sector_t block)
>
> ret = udf_dstrCS0toChar(sb, outstr, 31, pvoldesc->volIdent, 32);
> if (ret < 0) {
> - strcpy(UDF_SB(sb)->s_volume_ident, "InvalidName");
> + strscpy_pad(UDF_SB(sb)->s_volume_ident, "InvalidName");
> pr_warn("incorrect volume identification, setting to "
> "'InvalidName'\n");
> } else {
> - strncpy(UDF_SB(sb)->s_volume_ident, outstr, ret);
> + strscpy_pad(UDF_SB(sb)->s_volume_ident, outstr);
> }
> udf_debug("volIdent[] = '%s'\n", UDF_SB(sb)->s_volume_ident);
>
>
> ---
> base-commit: 928a87efa42302a23bb9554be081a28058495f22
> change-id: 20240401-strncpy-fs-udf-super-c-983457eb4ac3
>
> Best regards,
> --
> Justin Stitt <[email protected]>
>
--
Jan Kara <[email protected]>
SUSE Labs, CR